1. Field of the Invention:
The invention relates to a perforating gun for use in subterranean wells, and particularly to a perforating gun that will provide a full bore fluid or tool passage through the gun after discharge of the gun.
2. Summary of the Prior Art:
For many years the desirability of utilizing a subterranean well bore having a nonvertical or horizontal portion traversing a production formation, has been known and appreciated. Laterally directed bores are drilled regularly, usually horizontally, from the primary well bore to increase contact with the production formation which normally extends in a generally horizontal direction. When conventional vertical well bores are employed to tap wide area production formations, a large number of vertical bores must be employed. With the drilling of the well by having a non-vertical portion, even including a substantially horizontal portion, traversing the production formation, a much greater area of the production formation may be traversed by the well bore and drilling costs may be substantially decreased, After the horizontal well bore has produced all of the economically producible hydrocarbons, the same vertical well bore may be drilled to establish a horizontal portion extending in another direction and thus prolong the utility of the vertical portion of the well and increase the productivity capability of the well to include substantial areas of the production formation.
When a deviated well bore is extended into a production formation in a generally horizontal direction, it is no longer desirable to effect perforation of the well bore around the 360.degree. periphery of the well bore, as is the case in conventional vertical well bores. The reason for this is that upwardly directed perforations provide an opportunity for debris to fall into the fluid passage provided for removing production fluid from the perforated formation, and such debris tends to clog tool elements incorporated in the tubing string.
Special angular aligning arrangements have been heretofore proposed for insuring that the perforations are downwardly and horizontally directed.
A further problem arises in the utilization of conventional perforating guns in deviated well bores in that the disposition of the fired gun becomes a problem. In a normal vertical well, a vertical extension of the well, commonly called a "rat hole", is normally drilled to a sufficient depth beyond all production formations to permit the discharged gun to be dropped into the rat hole after the gun is fired and remain there. With a deviated well bore, particularly one traversing a production formation in a generally horizontal direction, the end of the formation may be many thousands of feet away from the region to be perforated and it is not desirable to fill up any portion of the well bore traversing a production formation with the discharged gun because subsequent operations may require those tool-filled portions be used for production. Additionally, there is a recognized problem that with a well bore having a horizontal or a slightly inclined configuration relative to the horizontal, there is little opportunity for a discharged perforating gun to drop any substantial distance before it becomes wedged in the well bore.
One last problem, which exists in conventional vertical wells as well as deviated wells, is that it is occasionally desirable to achieve the hydraulic fracturing of a perforated formation immediately after the firing of the perforating gun. This requires the transmission of a high pressure fracturization fluid to the perforated production zone of the well.
It is therefore highly desirable that a full bore passage be provided through a discharged perforating gun in order to conduct such high pressure fluid to the desired position for effecting a fracturization of the well bore. Furthermore, it is often desirable to insert other well tools, such as pressure and flow measuring indicators in the well bore beyond the perforating gun, and the conventional perforating gun, when discharged, interferes with the passage of such additional well tools.
There is therefore a definitive need in the oil well drilling industry for a perforating gun construction that will solve all of the aforementioned problems.